Swine Flu Deaths May Have Been 15 Times Higher Than Reported

The H1N1 virus was reported in more than 214 countries through August 2010, when the WHO declared an end to the pandemic. Photographer: Noah Seelam/AFP/Getty Images

June 26 (Bloomberg) -- The 2009 swine flu pandemic may have
killed 15 times more people globally than reported at the time,
according to the first study to estimate the death toll.

The H1N1 influenza virus probably killed about 284,500
people worldwide, compared with 18,500 deaths reported to the
World Health Organization, researchers from the U.S. Centers for
Disease Control and Prevention wrote in the journal Lancet
Infectious Diseases today. More than half the deaths may have
been in southeast Asia and Africa, compared with 12 percent of
officially reported fatalities, the authors wrote.

The estimate shows the difficulty in tracking the effect of
a pandemic as it’s unfolding, Cecile Viboud of the National
Institutes of Health and Lone Simonsen of George Washington
University wrote in an editorial. The WHO, which was criticized
for exaggerating the H1N1 threat, said during the outbreak that
the toll would end up being “unquestionably higher” than that
reported to it by national authorities.

“Laboratory-confirmed deaths are gross underestimates of
influenza-related mortality because of the lack of routine
laboratory tests and difficulties in identification of
influenza-related deaths,” they wrote.

The H1N1 virus was reported in more than 214 countries
through August 2010, when the WHO declared an end to the
pandemic. It’s since become one of three seasonal flu strains
circulating worldwide, causing infections mostly during the
winter months.

Mathematical Model

Seasonal influenza kills as many as 500,000 people every
year, according to the Geneva-based WHO. Those estimates are
typically based on the number of deaths above a country’s normal
death rate that coincide with a flu season.

Researchers led by Fatimah Dawood at the Atlanta-based
CDC’s influenza division developed a mathematical model using
data from 12 countries on flu cases that were diagnosed by a
patient’s symptoms alone, and not by a laboratory test. They
hypothesized that the risk of death is higher in some countries
than others.

Shortcomings in the availability of data in poorer
countries may affect the accuracy of the estimates, they said.

The number of deaths from the pandemic highlights the need
to expand production and improve delivery of vaccines to poorer
countries, which are often hardest hit by pandemics and lack the
resources to monitor diseases, the researchers wrote.

“The study underscores the significant human toll of an
influenza pandemic,” Dawood and colleagues said in an e-mailed
statement. “We hope that this work can be used not only to
improve influenza disease burden modeling globally, but to
improve the public health response during future pandemics in
parts of the world that suffer more deaths.”

Eighty percent of the deaths were probably in people
younger than 65 years, the authors wrote.